Sunscreen Maths: What You Need To Know

By Charlie Colville

1 week ago

1+1 = Summer Ready Skin


Are you applying your sunscreen correctly? And if you said ‘yes’, how can you be sure? SPF is an important daily step in our skincare routine, but we’re often not putting on enough (or any at all). And with summer just around the corner, the need for good sun protection is even more imperative. But thankfully, we have a simple, handy way of remembering what we need: sunscreen maths.

Sunscreen Maths: How To Properly Apply SPF

Despite UK skin cancer rates sitting at their highest in recent years, it’s estimated that almost 70 percent of British people don’t actually use enough sunscreen to get the full protection needed to protect their skin. ‘SPF, or Sun Protection Factor, is a measure of protection against UVB rays, which are primarily responsible for sunburn,’ says Dr Sophie Momen, Consultant Dermatologist at the Cadogan Clinic. ‘SPF50, for instance, means that it takes the skin 50 times longer to burn when wearing sunscreen than without. However, most people apply less than a fifth of the recommended amount of sunscreen, significantly reducing its effectiveness.

‘By applying the correct amount of sunscreen and ensuring full coverage, you significantly reduce the risk of skin cancer and other sun-related skin damage, including accelerated ageing,’ she continues. ‘Proper education and awareness about effective sunscreen application are crucial steps in combating the rising rates of skin cancer.’

Overhead view of beach

(c) Alex Perez, Unsplash

So, how much SPF should we be applying? And where? Dr Momen has devised the perfect sunscreen maths lesson to get us started.

What Is Sunscreen Maths?

Sunscreen maths is a handy formula for remembering how much and where to apply your SPF. It features 11 areas, two fingers and four forgotten areas – just think of it as the 11-2-4 SPF method.

11 Areas

There are 11 specific areas that the body can be divided into when applying sunscreen. These are:

  1. Head, face, and neck
  2. Left arm
  3. Right arm
  4. Upper back
  5. Lower back
  6. Chest
  7. Stomach
  8. Left upper leg and thigh
  9. Right upper leg and thigh
  10. Lower left leg and foot
  11. Lower right leg and foot

2 Fingers

How much sunscreen do we actually need to put on? ‘To achieve adequate SPF coverage, the correct amount of sunscreen is 2mg/cm, but unfortunately, many people fall short of this, leaving their skin vulnerable to damage,’ says Dr Momen. It’s not very efficient to measure out this precise measurement, so instead Dr Momen recommends using two fingers worth (the length of each finger) of SPF on each body part.

4 Forgotten Areas

The last part of the sunscreen maths formula concerns those often-forgotten areas; we’re talking ears, temples, neck and feet. Since these areas are more prone to being left behind, it’s important to keep them in mind when applying SPF.

Featured image: Gryffyn M, Unsplash